The Wizard of Oz by Ted Eshbauch. 30's cartoon. Filmed in Technicolor, but released in Black-and-White due to licensing issues. It has everything. Weird rubbery animation? Check. A creepy wizard? Check. Strange plot and imagery? Check, Check. A very Creepy Cartoon.

Although they weren't in the same league as some of the others mentioned here, I always thought Ren & Stimpy were disturbing as hell. Once I was trying to calm down a friend of mine who showed up at my house around midnight in the summer of '96 saying he'd taken LSD and he wanted to watch Ren & Stimpy because he said it'd mellow him out. (He kept asking for sofa cushions to be stacked up behind his head so it wouldn't fall off, and also wanted ice water by the pitcher, and I was just trying to get him to talk quietly and not wake my dad upstairs.) So Ren & Stimpy calmed him on drugs but made me creeped out stone cold sober. Such a gross cartoon. Ye gods I still hate that show...